This application claims the priority of Korean Patent Application No. 2003-43572, filed on Jun. 30, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a display method, and more particularly, to a method of automatically setting image quality such that brightness (that is, a cut off point) and contrast (that is, a saturation point) of an actual image are maintained at a constant level regardless of a status of an input signal.
2. Description of the Related Art
In a conventional auto gain control (AGC) method, which processes an input video signal after converting a level of the input video signal that exceeds a reference value, the video signal is compensated for based on a sync level, which is combined with the video signal before being input. Therefore, it is difficult to exactly compensate for the brightness of an actual image. Also, a malfunction of a device performing the AGC process may occur, during which the AGC process cannot exactly compensate for the signal level.
Image quality of a broadcast signal and images received from video tapes may be different from each other. Also, image quality of a video signal and of a digital versatile disc (DVD) signal, which are connected to a same DVD player, may be different from each other. Most users usually watch the images as they are. However, some users adjust the brightness and contrast of the image by accessing a user menu. However, the adjustments should be made automatically when the channel is changed or input source is changed.
FIGS. 1A and 1B are flow charts illustrating a conventional method for setting image quality.
Referring to FIG. 1A, a brightness signal included with an input video signal is converted into an 8-bit digital signal (step 100). The digital brightness signal is stored in one of a register 50h through a register 6Fh according to a brightness level (step 101). The digital brightness signal is input to a scaler (not shown). The upper 4 bits of the 8-bit digital brightness signal are divided into 16 levels according to the brightness level, and resultant values of the division are stored in register 51h through register 6Fh in 2-byte units. That is, the darkest digital brightness signal is stored in register 50h and register 51h, and the brightest digital brightness signal is stored in register 6Dh and register 6Fh.
Values of registers 51h/53h/6Dh/6Fh, which are the registers that compensate image quality, are read to determine whether the values of the registers 51h/53h/6Dh/6Fh are 0x00/0xHH/0xHH/0x00 (steps 102 and 103). Here, 0xHH does not refer to a specific value, but satisfies 0xHH≠0x00.
When the values of registers 51h/53h/6Dh/6Fh are 0x00/0xHH/0xHH/0x00, it is determined that the image quality is set to be optimal, and corresponding brightness and contrast values are stored in memory (step 104).
When the values of registers 51h/53h are 0x00/0x00, the brightness value of an output video signal is decreased by one level (steps 105 and 106).
However, when the values of registers 51h/53h are 0xHH/0xHH, the brightness value of the output video signal is increased by one level (steps 107 and 108).
In addition, when the values of registers 6Dh/6Fh are 0x00/0x00, the contrast value of the output video signal is increased by one level (steps 109 and 110).
However, when the values of registers 6Dh/6Fh are 0xHH/0xHH, the contrast value of the output video signal is decreased by one level (steps 111 and 112).
As described above, the brightness/contrast may be changed excessively depending on the status of the image when a cut off level and a saturation level are compensated for by changing the brightness/contrast according to conventional methods, thus a method of preventing this is required.
For example, when it is assumed that a night scene is displayed, the dark scene may be displayed too brightly such that a viewer cannot determine whether the scene is a night scene or a day scene, by increasing the contrast to a high level. In this case, there is a need to prevent the contrast from increasing beyond a certain maximum point, to represent the night scene appropriately.